If you want to ask kiwi yachties directly then try posting a question on crew.org.nz ... a NZ based sailing forum.

There will likely be opportunities to crew on yachts for short evening races (rum races) on weekday evenings or for day sails there are charter boat companies that will charter a yacht either bare boat or skippered. Alternatively, there is an opportunity to go sailing on an America's Cup class yacht in Auckland.